Does frozen food last longer in a manual defrost freezer as opposed to a frost-free model?

I ask this because, it seems that the freezer in my fridge doesn't keep frozen food very long at all, and it is frost-free. I'm thinking that it might be better for the preservation of frozen food to buy a manually defrosting freezer and not have a problem concerning a freezer choosing the frost-free function to the detriment of the "keeping foods frozen" function.